Certain flat panel displays such as liquid crystal displays and the like do not produce light themselves. Illumination (ambient light or a special light source) is therefore needed in order to produce visible images for such a display. Edge-lighting is a form of illumination used in displays including liquid crystal displays (LCDs), active matrix liquid crystal displays (AMLCDs) or the like. For an edge-lit display, light sources may be arranged along the edges of the display panel and may illuminate the center and other areas of the screen using light guides. Light-emitting diodes (LEDs) may be used for providing edge-lighting for such displays.
The displays used in some applications may be required to be compatible with night vision imaging systems (NVIS). For instance, certain avionics and/or ground vehicle displays not only need to be visible to unaided eyes, but also need to be compatible with night vision equipment (e.g., night vision goggles) without adversely affecting the operation of the night vision equipment. Traditional NVIS compatible LED edge-lights are typically single mode in operation with all of the LEDs being filtered by complex and expensive thin film filters. These single mode edge-lights are limited by luminance loss as well as color uniformity issues due to the filtering variance of the emitters over angle through the thin film filters. Other NVIS compatible edge-light approaches have exhibited problems such as extreme color variations or luminance non-uniformities. Therein lies a need for a night vision compatible LED edge-light that overcomes these shortcomings.